Just messing around with it for a few minutes...
They give you "what to expect" when you click on certain areas at a specific level of magnification.
Zoomed fairly far out you can still see coverage detail on the 2G/Voice tab.
On 4G/3G tab you can see the new towers, where 2G is still at and how 4G/3G is expanding and where it is at.
More detailed coverage description, and roaming coverage is now in yellow.
Gives names of subdivisions, too.
3G/4G maps show roaming on a nationwide scale.
Overall, this is the best personal coverage checker map I've seen on any carrier!
My question is when on 2G/Voice tab I see the yellow "service partner" areas, then I also see great areas that say "no service" - I wonder if that is 911 only? Because, they also have places that are just not marked at all.